In recent years, domestic main illumination apparatuses such as ceiling lights using light emitting diodes (LEDs) as a light source has been in wide use. FIG. 6 shows such one conventional illumination apparatus 101. The illumination apparatus 101 includes an illumination module (not shown) including LEDs as a light source; a transparent cover 102 which transmits light from the illumination module; a housing 103 which holds the illumination module and the transparent cover 102; and a center cover 104 which is made of an opaque material and covers a central portion of the housing 103. In the central portion of the housing 103 covered with the center cover 104, there are provided a power supply unit which supplies a power to the illumination module and an apparatus attachment part which fixes the illumination apparatus to a ceiling. Light from the illumination module is outputted through the entire surface of the transparent cover 102.
In the illumination apparatus shown in FIG. 6, the center cover 104 is provided in the central portion of the illumination apparatus 101, and thus no light is emitted from this central portion. For that reason, when the illumination apparatus 101 is turned on, the central portion becomes dark, and thus the illumination apparatus 101 shows poor visual quality as compared to, e.g., conventional ceiling lights using a ring-like fluorescent lamp as a light source.
Apart from the above, there has been proposed an illumination apparatus in which a light guide plate and a reflector are used to emit light from light sources through the central portion of the illumination apparatus in order to increase an emission area without increasing the number of light sources (see, e.g., Japanese Patent No. 4066702). In this illumination apparatus, some of the lights from the light sources arranged on the circumference near the inner periphery of a lamp housing are inserted into the light guide plate and led to the central portion of the illumination apparatus. Then, the lights outputted to the light guide plate are reflected by the reflector arranged in the lamp housing side of the light guide plate and are outputted in a light irradiation direction through a transmitting part of the light guide plate.
However, in the illumination apparatus disclosed in Japanese Patent No. 4066702, the light guide plate and the reflector overlap with each other in the light irradiation direction and some of the lights incident from the light sources into the light guide plate shuttles between the light guide plate and the reflector, which shows low light use efficiency.